Back in the 1980's I was really into Z80 programming on the ZX81. I had a book that was my go to reference for programming but sadly over the years it got lost and I have forgotten the title. At first I thought it may be Toni Baker's Mastering Machine Code on Your ZX81 but after firing up the old brain cells I don't remember any of that in the book.

What I do remember is that it went deep into the structure of Basic and the ROM. It showed the layout of the Basic Line, the variable area and the format of the variable types. The part I found most invaluable was a listing of Rom routines and how to implement them. All the routines showed what the registers needed calling the routines and what were in them after the routines ended. I believe there were routines for binary to 4 digit "ZX ASCII", running one line of code, address of a Basic variable, next line number and so forth. Now I know it was a white cover with possibly red lettering so it may be Byteing Deeper into Your Timex Sinclair 1000 by Mark Harrison but without an index I can't confirm it.

What I'm really looking for is the list of ROM routines in that book so if there is a pdf of that part it would be great. I do have The Explorer's Guide to the ZX81 and Timex Sinclair 1000 by Mike Lord that also has a rom routine listing but isn't as comprehensive.

Back in the 1980's I was really into Z80 programming on the ZX81. I had a book that was my go to reference for programming but sadly over the years it got lost and I have forgotten the title. At first I thought it may be Toni Baker's Mastering Machine Code on Your ZX81 but after firing up the old brain cells I don't remember any of that in the book.

What I do remember is that it went deep into the structure of Basic and the ROM. It showed the layout of the Basic Line, the variable area and the format of the variable types. The part I found most invaluable was a listing of Rom routines and how to implement them. All the routines showed what the registers needed calling the routines and what were in them after the routines ended. I believe there were routines for binary to 4 digit "ZX ASCII", running one line of code, address of a Basic variable, next line number and so forth. Now I know it was a white cover with possibly red lettering so it may be Byteing Deeper into Your Timex Sinclair 1000 by Mark Harrison but without an index I can't confirm it.

What I'm really looking for is the list of ROM routines in that book so if there is a pdf of that part it would be great. I do have The Explorer's Guide to the ZX81 and Timex Sinclair 1000 by Mike Lord that also has a rom routine listing but isn't as comprehensive.

Whilst I can't help with the book, this page may be useful if all you want are the ROM explanations.

Thanks for all the replies and references. Looking at the contents of the Byteing Deeper book I can tell that wasn't the book I was thinking about. I believe the cover had only the title with no graphics. I had it for an Assembly Coding SIG I was in in 1985 when I was in the Capitol Area Timex Sinclair User Group in Washington DC.